Many human transactions involve strangers. They have never interact with each other before, thus need a way to verify that the persons they are interacting with are authorized to conduct the transactions. Most the time, physical identification documents issued by an authority are used as means to authenticate a person. Examples are driver licenses issued by the government, credit cards issued by a bank, and even business cards issued by a company. However, there are times when a person does not have possession of a physical identification document. Thus, it is important to develop a system to authenticate a person without the need to rely on physical identification documents.